Objective To study the drug diffusion process in posterior eye under the biodegradation behavior of hydrogels, and to provide the research basis for evaluating local drug concentration and optimizing intraocular drug release performance of the biodegradable hydrogels. Methods Through finite element analysis, the drug delivery model of the biodegradable drug-loaded in-situ hydrogels in posterior eye was established. The effects of degradation of hydrogels, intraocular pressure and convection caused by active absorption of retinal pigment epithelial cells, as well as the effect of intraocular absorption and clearance on drug diffusion were considered to study the development of drug concentration in posterior eye. Results The intraocular drug diffused mainly to the posterior segment during drug release, and release rate of the drug-loaded hydrogels was significantly slower than that of the solution. Conclusions The biodegradable hydrogels prolong the residence time of drug in posterior eye by preventing movement of the drug center and limiting drug diffusion inside the hydrogels. Reasonable adjustment of the in-situ hydrogel injection position and degradation performance parameters can effectively improve its therapeutic effects.